a. Field of the Invention
This disclosure relates to a system and method for assessing the formation of a lesion in tissue. More particularly, this disclosure relates to a system and method for assessing the depth of a lesion formed in the tissue, the likelihood a lesion has reached a predetermined depth, and/or the temperature of the tissue during an ablation procedure being performed on the tissue.
b. Background Art
It is known that ablation therapy may be used to treat various conditions afflicting the human anatomy. One such condition that ablation therapy finds particular applicability is in the treatment of atrial arrhythmias, for example. When tissue is ablated, or at least subjected to ablative energy generated by an ablation generator and delivered by an ablation catheter, lesions form in the tissue. More particularly, electrode mounted on or in the ablation catheter are used to create tissue necrosis in cardiac tissue to correct conditions such as atrial arrhythmia (including, but not limited to, ectopic atrial tachycardia, atrial fibrillation, and atrial flutter). Atrial arrhythmias can create a variety of dangerous conditions including irregular heart rates, loss of synchronous atrioventricular contractions and stasis of blood flow which can lead to a variety of ailments and even death. It is believed that the primary cause of atrial arrhythmia is stray electrical signals within the left or right atrium of the heart. The ablation catheter imparts ablative energy (e.g., radio frequency energy, cryoablation, lasers, chemicals, high-intensity focused ultrasound, etc.) to cardiac tissue to create a lesion in the cardiac tissue. The lesion disrupts undesirable electrical pathways and thereby limits or prevents stray electrical signals that lead to arrhythmias.
One challenge with ablation procedures is in the assessment of the lesion formation as a result of the application of ablative energy to the tissue. For example, it is difficult to evaluate, assess, and/or determine the depth of a lesion in the tissue. As such, it is difficult to determine whether the tissue has been sufficiently or acceptably ablated, or at least whether a lesion has reached a desired depth. Lesion formation has typically been fairly crudely assessed.
For example, conventional techniques to assess lesion formation, and particularly, lesion depth, have included monitoring the impedance on the ablation generator and monitoring electrogram reduction as the ablation procedure is performed and progresses. However, conventional techniques have proved to be less than optimal as none of the conventional techniques provide an accurate means by which the depth of a lesion, for example, can be predicted with any real certainty.
Accordingly, the inventors herein have recognized a need for a system and method for assessing lesion formation in tissue as a result of an ablation procedure being performed thereon that will minimize and/or eliminate one or more of the deficiencies in conventional ablation systems.